Preparation And Performance Study Of Water-soluble Temporary Plugging Agents

Three crosslinking agents were uesd for the fabrication of temporary plugging agents.Furthermore,properties of as-prepared products such as absorption rate and dissolved time were studied.(1) Aluminum nitrate was used as cross-linking agent for the preparation of water-soluble cross-linker plugging agent.Through the absorption rate comparison analysis of temporary plugging agent agent, the best preparation conditions is as follows : when dosage of acrylamide is 5 g, cyclohexane is 60.00 mL, Span-60 is 0.80 g and Tween-60 is 0.40 g, the neutralization degree is 80 %, starch is 1.50 g, aluminum nitrate is 0.02 g, experiment temperature is 70℃and reaction lasts for 3h.(2) Polypropylene glycol diglycidyl ether was used as cross-linking agent (the compressive strength of temporary plugging agent is improved through long chain structure) and the influence of water absorption was investigated with or without anhydrous sodium carbonate, the best preparation condition is as follows: the dosage of cyclohexane is 60.00 mL, Span-60 is 0.80 g and Tween-60 is 0.40g, the neutralization degree is 80 %, dosage of acrylamide is 4g, starch is 2.0 g, polypropylene glycol diglycidyl ether is 0.02 g, Sodium carbonate is 1.0 g, experiment temperature is 70℃and reaction lasts for 3h.(3) The water-soluble temporary plugging agents were prepared with cross-linking agent made by ourselves, and performance of temporary plugging agents were studied. The conclusions are as fllows: the solubility of monomer A-monomer B polymer-based temporary plugging agent improves significantly by the addition of monomer C. The intensity and solubility of temporary plugging temporary plugging increase with the addition of monomer C, because more monomer as activity center can form physical cross-linking structure, which can improve the intensity of composite materials. When monomer C content increased, more polymers exist as intercalated form, molecular weight of polymer decreases and the winding of polymer molecular chain reduces, which effectively promote the dissolution of the composite materials. The best ratio of the main materials and the supporting materials is 20:7:10:1 through experiments. (4) By comparison, homemade cross-linking agent is chosen for preparation of temporary plugging agents as oilfield pilot test products, and indoor tests have been carried out. The results show that: the composite temporary plugging agent is prepared which can meet the requirements of repeated fracturing technology of old wells, the as prepared temporary plugging agent can cause water-absorbing swelling and expansion, then forms soft particles when it soaks in water, which can adapt strata passageways of different sizes, can rapidly seal high permeability layer and has no requirements on size of the strata pore canal; the as prepared temporary plugging agent has good water absorption and is easy to dissolve, which can dissolve in water to 100 % in 2 h at 60℃,has limited effect on fracturing operation; its sedimentation velocity and support agent are an order of magnitude, it is also easy for liquid carrying; As prepared temporary plugging agent can quickly dissolve at different temperature conditions in different medias like formation water, 0.5 % guar gum cross-linking fracturing fluid and water cut oil (water content is 55 %), and the properties are stable, which has good compatibility with guar gum cross-linking fracturing fluid,it is easy for liquid carrying; Under pressure of 60MPa ,the breaking rate is relatively low, can satisfy the requirement of anti pressure in fracturing process; the chosen materials are all environment friendly materials, the temporary plugging agent waste won't cause pollution to the environment, and has no significant influence on oil and gas exploration, which can assure the safety of equipment and shaft when downhole construction are carrying on.(5) According to the field application test, the conclusion can be summarized as follows: the on-site application of the temporary plugging agent is successful, which can effectively realize temporary plugging, the as prepared temporary plugging agents are added in, after artificial fracture bridge plugging, crack steering can easily occur; as prepared temporary plugging agents have low price with stable performance and good compatibility with other liquids; The technique of as prepared temporary plugging agent used in temporary plugging fracturing technology is very simple, single-well control agent consumption is low, it has very important significance to well productivity improvement and fully use of old wells.